Textile treatment compositions suitable for providing fabric softening and static control benefits during laundering are well-known in the art and have found wide-scale commercial application. Conventionally, rinse-added fabric softening compositions contain, as the active softening component, substantially water-insoluble cationic materials having two long alkyl chains. Typical of such materials are di-tallow di-methyl ammonium chloride and imidazolinium compounds subhstituted with two stearyl groups. These materials are normally prepared in the form of a dispersion in water. It is generally not possible to prepare such aqueous dispersions with more than about 10% of cationic materials without encountering intractable problems of product viscosity and stability, especially after storage at elevated temperatures, such that the compositions are unpourable and have inadequate dispensing and dissolving characteristics in rinse water. This physical restriction on softener concentration naturally limits the level of softening performance achievable without using excessive amounts of product, and also adds substantially to the costs of distribution and packaging. Accordingly, it would be highly desirable to prepare physically-acceptable textile treatment compositions containing much higher levels of water-insoluble cationic softener materials.
It would also be desirable to have fabric softening compositions which are storage-stable, and also which are biodegradable. However, materials which may be biodegradable are often difficult to formulate as stable liquid compositions.
It is an object of this invention to provide a storage-stable, biodegradable fabric softening composition. It is a further object to provide such materials in the form of liquid products, including concentrates, suitable for use in the rinse cycle of a textile laundering operation, and in sheet form for use in clothes dryers. These and other objects are obtained using the present invention, as will be seen from the following disclosure.
Cationic softener materials are normally supplied by the manufacturer in the form of a slurry containing about 70%-80% of active material in an organic liquid such as isopropanol, sometimes containing a minor amount of water (up to about 10%). Retail fabric softening compositions are then prepared by dispersion of the softener slurry in warm water under carfully controlled conditions. The physical form and dispersibility constraints of these industrial concentrates, however, are such as to preclude their direct use by the domestic consumer; indeed, they can pose severe processing problems even for the industrial supplier of retail fabric softening compositions.
The use of various quaternized ester-amines as cationic fabric softening agents is known in the art. See, for example, U.S. Pat. No. 4,339,391, Hoffmann, et al., issued July 13, 1982, for a series of quaternized ester-amines which function as fabric softeners. Various quaternized ester-amines are commercially available under the tradenames SYNPROLAM FS from lCl and REWOQUAT from REWO. Similarly, methods for preparing various quaternized ester-amine compounds are known in the art. See, for example, U.S. Pat. No. 3,342,840, Sobolev, issued Sept. 19, 1967, U.S. Pat. No. 3,872,138, Ogatu, issued Mar. 18, 1975, and Japanese Laid Open Publication No. 49-1510, assigned to Gosei Chem. Ind. Co., published Jan. 9, 1974.
Unfortunately, although quaternized ester-amines are believed to be rapidly biodegradable, they are more subject to hydrolysis than are conventional cationic softening agents (e.g., ditallow dimethyl ammonium chloride and analogs thereof) and hence can encounter hydrolytic stability problems upon prolonged shelf storage. The product stability and viscosity problems becoming increasingly more unmanageable in concentrated aqueous dispersions.
Various solutions to the problem of preparing concentrated fabric softening compositions suitable for consumer use have been addressed in the art. See, for example, U.S. Pat. Nos. 4,426,299, issued Jan. 17, 1984, and 4,401,578, issued Aug. 30, 1983, Verbruggen, which relate to paraffin, fatty acids and ester extenders in softener concentrates as viscosity control agents.
European Patent No. 0,018,039, Clint, et al., issued Mar. 7, 1984, relates to hydrocarbons plus soluble cationic or nonionic surfactants in softener concentrates to improve viscosity and stability characteristics.
U.S. Pat. No. 4,454,049, MacGilp, et al., issued June. 12, 1984, discloses concentrated liquid textile treatment compositions in the form of isotropic solutions comprising water-insoluble di-C.sub.16 -C.sub.24 optionally hydroxy-substituted alkyl, alkaryl or alkenyl cationic fabric softeners, at least about 70% of the fabric softener consisting of one or more components together having a melting completion temperature of less than about 20.degree. C., a water-insoluble nonionic extender, especially C.sub.10 -C.sub.40 hydrocarbons or esters of mono- or polyhydric alcohols with C.sub.8 -C.sub.24 fatty acids, and a water-miscible organic solvent. The concentrates have improved formulation stability and dispersibility, combined with excellent fabric softening characteristics.
U.S. Pat. No. 4,439,330, Ooms, issued Mar. 27, 1984, teaches concentrated fabric softeners comprising ethoxylated amines.
U.S Pat. No. 4,476,031, Ooms, issued Oct. 9, 1984, teaches ethoxylated amines or protonated derivatives thereof, in combination with ammonium, imidazolinium, and like materials. The use of alkoxylated amines, as a class, in softener compositions is known (see, for example, German Patent Applications Nos. 2,829,022, Jskobi and Schmadel, published Jan. 10, 1980, and 1,619,043, Mueller et al., published Oct. 30, 1969, and U.S. Pat. Nos. 4,076,632, Davis, issued Feb. 28, 1978, and 4,157,307, Jaeger and Davis, issued June 5, 1979).
U.S. Pat. No. 4,422,949, Ooms, issued Dec. 27, 1983, relates to softener concentrates based on ditallow dimethyl ammonium chloride (DTDMAC), glycerol monostearate and polycationcs.
In United Kingdom Application No. 2,007,734A, Sherman et al., published May 23, 1979, fabric softener concentrates are disclosed which contain a mixture of fatty quaternary ammonium salts having at least one C.sub.8 -C.sub.30 alkyl substituent and an oil or substantially water-insoluble compound having oily/fatty properties. The concentrates are said to be easily dispersed/emulsified in cold water to form fabric softening compositions.
Concentrated dispersions of softener mateerial can be prepared as described in European Patent Application No. 406 and United kingdom Patent Specification No. 1,601,360, Goffinet, published Oct. 28, 1981, by incorporating certain nonionic adjunct softening materials therein.
As can be seen, the various solutions to the specific problem of preparing fabric softening compositions in concentrated form suitable for consumer use have not been entirely satisfactory. It is generally known (for example, in U.S. Pat. No. 3,681,241, Rudy, issued Aug. 1, 1972) that the presence of ionizable salts in softener compositions does help reduce viscosity, but this approach is ineffective in compositions containing more than about 12% of dispersed softener, inasmuch as the level of ionizable salts necessary to reduce viscosity to any substantial degree has a seriously detrimental effect on product stability.
It has now been discovered that fabric softener compositions, especially concentrated compositions, containing the specific quaternized hydroxypropyl monoester ammonium salts of the present invention possiss desirable product stability and viscosity characteristics. Moreover, neither the use of these specific compounds in laundry fabric softening compositions, nor the desirable fabric softener/viscosity/stability/biodegradability properties of fabric softening compositions containing these compounds, including concentrates, appear to have been appreciated heretofore.